A vitreous silica crucible is used for pulling single-crystal silicon. The inner portion (inner surface layer) of this vitreous silica crucible is formed of a transparent glass layer including substantially no bubbles because it has to be in contact with a silicon melt, and both outer portions (outer surface layers) are formed of a bubble-containing layer including a number of bubbles in order to disperse outword radiation heat and uniformly transfer the heat to the inside of a mold.
A rotary mold method has been known from the past as a method of manufacturing the above-mentioned vitreous silica crucible. This manufacturing method is a method of manufacturing a crucible by heating a vitreous silica powder accumulated on the inner surface of a rotary mold from the space side of a mold for vitrification, wherein during this heating and melting, vacuuming is performed to remove bubbles in a glass layer by sucking air in the vitreous silica powder-deposited layer from the mold side to reduce the pressure, thereby forming an inner surface layer formed of a transparent glass layer containing substantially no bubbles (JP-A No. 56-149333 and JP-A No. 01-148782).
In recent years, the temperature of a crucible during pulling tends to become higher with an increase in the size of a crucible. When the temperature of a crucible rises, the viscosity of glass is reduced, and as a result, the crucible possibly deforms during use. As a measure against this, a method of enhancing the strength by applying or containing a crystallization accelerator for glass to the surface, which allows the crucible to crystallize the glass under high temperature is known.
More specifically, it is described in JP-A No. 8-2932 that a crystallization accelerator (alkali metals, alkaline earth metals or the like) is applied to the surface of the inner surface layer of a vitreous silica crucible, or is contained in the inner surface layer, and the crystallization accelerator of the inner surface layer of the crucible is crystallized early as a nucleus when used. In addition, it is described in JP-A No. 11-199370 that a vitreous silica layer prevents the crystallization accelerator from coming into contact with a silicon melt by forming a layer containing a crystallization accelerator under the inner surface layer constructed of transparent glass. Furthermore, it is described in JP-A No. 2003-95678 that a crystallization accelerator is attached to the outer surface layer in addition to the inner surface layer of a crucible to increase the inner surface layer and the dimensional stability.